1 evaluation / usability usability is it a “good” interface? in what ways? usability: how well...

1

Evaluation / Usability

Usability Is it a “good” interface?

In what ways? Usability:

How well users can use the system’s functionality

How well can the interface be used – it’s just that simple

5Original

6Proximity

7Repetition

Examples of Bad Design … and Why

Elevator controls and labels on the bottom row all look the same, so it is easy to push a label by mistake instead of a control button

People do not make same mistake for the labels and buttons on the top row. Why not?

Logical or ambiguous design?

Where do you plug the mouse?

Where do you plug the keyboard?

top or bottom connector?

Do the color coded icons help?

From: www.baddesigns.com

Internal and external consistency Internal consistency refers to designing

operations to behave the same within an application Difficult to achieve with complex interfaces

External consistency refers to designing operations, interfaces, etc., to be the same across applications and devices Very rarely the case, based on different designer’s

preference Most successful in product families (e.g MS Office) Op. Sys. vendors may define style guidelines

External Inconsistency …

Keypad numbers layout

1 2 34 5 6

7 8 9

7 8 9

1 2 3

4 5 6

0 0

(a) phones, remote controls (b) calculators, computer keypads

Usability Problem Example: Unexpected Occurrence of Events

Usability Measures – 5 Often Used Time to learn

How long does it take for typical members of the community to learn relevant task?

Speed of performance How long does it take to perform relevant benchmarks?

Rate of errors by users How many & what kinds of errors are made during

benchmark tasks? Retention over time

Frequency of use and ease of learning help make for better user retention

Subjective satisfaction Do they like it? Allow for user feedback via interviews, free-form

comments and satisfaction scales

16Original

compliant interaction

state evident inmechanical buttons

rotary knobs reveal internal state and can be controlled by both user and

machine

Evaluation TechniquesEvaluation

tests usability and functionality of system occurs in laboratory, field and/or in

collaboration with users evaluates both design and

implementation

19

Questionnaire Design Collect general demographic information that

may be relevant Age, sex, computer experience, etc.

Evaluate feelings towards your product and other products

Important to design questionnaire carefully Users may find questions confusing

May not answer the question you think you are asking May not measure what you are interested in

20

Questionnaire, 2 “Likert scale”

Propose something and let people agree or disagree:agree disagree

The system was easy to use: 1 .. 2 .. 3 .. 4 .. 5 “Semantic differential scale”

Two opposite feelings:difficult easy

Finding the right information was: -2 .. -1 .. 0 .. 1 .. 2 If multiple choices, rank order them:

Rank the choices in order of preference (with 1 being most preferred and 4 being least): Interface #1 Interface #2 Interface #3 Interface #4 (in a real survey, describe the interfaces)

21

Survey example

Subject ID: ____________

An Experimental Study on various input techniques

Questionnaire

Please complete the following questionnaire. Please feel free to ask any

questions.

1. Please rate each input method. 1. Mouse

terrible very poor poor OK good very good great

-3 -2 -1 0 1 2 3 2. Tapping on the SmartBoard


-3 -2 -1 0 1 2 3 3. Using a Laser Pointer in one hand with the button in the other


-3 -2 -1 0 1 2 3 4. Using a Laser Pointer built into a Palm (Symbol) device


-3 -2 -1 0 1 2 3 5. Using a stylus on the PocketPC device


-3 -2 -1 0 1 2 3

6. Remote control joystick provided with the projector

1. Please rank order your preference, using 1 for most preferred and 6 for least: Mouse Tapping on the SmartBoard Using a Laser Pointer in one hand with the button in the other Using a Laser Pointer built into a Palm (Symbol) device Using a stylus on the PocketPC device Remote control joystick provided with the projector

2. Please rate your proficiency in using computers.

Never used before Novice Expert

0 1 2 3 4 5 6 7

3. Please rate your proficiency in using a Palm Pilot or other PDA.


0 1 2 3 4 5 6 7

4. Please rate your proficiency in using a laser pointer in general (not necessarily tracked by the computer).


0 1 2 3 4 5 6 7

5. Please rate your proficiency in using a touch sensitive whiteboard like the SmartBoard.


0 1 2 3 4 5 6 7

6. Do you own a Palm Pilot or other Personal Digital Assistant (PDA)? If so, which model?

Yes, I have a:

No

7. Please supply some information about yourself:

Male Female Age: 8. Please write down any other comments or suggestions for improvement: __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________

- End -

22

Where Evaluate? Usability Labs

Cameras, 2-way mirrors,specialists

Separate observationand control room Should disclose who is watching

Having one may increase usability evaluations in an organization

Can usually perform an evaluation anywhere Can use portable videotape recorder, etc.

Cognitive Walkthrough

Proposed by Polson et al. evaluates design on how well it supports

user in learning task usually performed by expert in cognitive

psychology expert ‘walks though’ design to identify

potential problems using psychological principles

Cognitive Walkthrough

Example: Code walkthrough in Software Engineering

To review a segment of program code by the expert other than programmer

Sequence of actions Selecting a set of program codes Check certain characteristics, such as, coding style,

spelling variables conventions, function declarations, system-wide invariants etc.

Cognitive Walkthrough (ctd)

For each task walkthrough considers what impact will interaction have on user? what cognitive processes are required? what learning problems may occur?

Analysis focuses on goals and knowledge: does the design lead the user to generate the correct goals?

26

Questions Cognitive Walkthrough

1. Is the next goal clear at this stage?2. Is the appropriate action obvious?3. Is it clear that this action leads to the goal?4. What problems are there in performing the

action?

Cognitive Walkthrough: How (cont.) Walk through the task while answering these

Questions: Will the user know what to do? Will the user see how to do it? Will the user understand from feedback whether

their action was correct?

Heuristic Evaluation Proposed by Nielsen and Molich.

usability criteria (heuristics) are identified design examined by experts to see if these are

violated Example heuristics

system behaviour is predictable system behaviour is consistent feedback is provided

Heuristic evaluation `debugs' design.

The Procedure Several independent evaluators

each uses the same checklist each works alone each makes a list of usability problems

Combine lists into a single list works well as a group activity

HE: 10 Usability Heuristics

1. Visibility of system status The system should always keep users informed about what is going

on, through appropriate feedback within reasonable time

2. Match between system and the real world The system should speak the users' language, with words, phrases and

concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order

3. User control and freedom Users often choose system functions by mistake and will need a

clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. Support undo and redo

HE: 10 Usability Heuristics4. Consistency and standards

Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions

5. Error prevention Even better than good error messages is a careful design which

prevents a problem from occurring in the first place

6. Recognition rather than recall Make objects, actions, and options visible. The user should not have

to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate

HE: 10 Usability Heuristics7. Flexibility and efficiency of use

Accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions

8. Aesthetic and minimalist design Dialogues should not contain information which is irrelevant or rarely

needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility

9. Help users recognize, diagnose, and recover from errors Error messages should be expressed in plain language (no codes),

precisely indicate the problem, and constructively suggest a solution

HE: 10 Usability Heuristics10. Help and documentation

Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large

Jacob Nielsen originally developed the heuristics for heuristic evaluation in collaboration with Rolf Molich in 1990. Nielsen since refined the heuristics based on a factor analysis of 249 usability problems to derive a set of heuristics with maximum explanatory power, resulting in this revised set of heuristics

34

“Think Aloud” Protocols “Single most valuable usability engineering method” Find out why user does things

What thought would happen, why stuck, frustrated, etc. Encourage users to expand on whatever interesting But interferes with timings May need to “coach” user to keep talking

Unnatural to describe what thinking Ask general questions: “What did you expect”, “What

are you thinking now” Not: “What do you think that button is for”, “Why didn’t you click

here” Will “give away” the answer or bias the user

Alternative: have two users and encourage discussion

Physiological measurements emotional response linked to physical

changes these may help determine a user’s reaction

to an interface measurements include:

heart activity, including blood pressure, volume and pulse.

electrical activity in brain: electroencephalogram (EEG)

Eye tracking head or desk mounted equipment tracks the

position of the eye eye movement reflects the amount of cognitive

processing a display requires measurements include

fixations: eye maintains stable position. Number and duration indicate level of difficulty with display

saccades: rapid eye movement from one point of interest to another

scan paths: moving straight to a target with a short fixation at the target is optimal

Reality …

39

Example:prompts

What is a DTIC user code and how to get one?

40

Example: prompts (Print)

Keystroke-Level Model (KLM)

KLM OperatorsK Press a key or button

P Point to a target on the display

H Home hands on input device

D Draw a line segment

M Mentally prepare for an action

R (system response time)

Example: Replacing a Word

Operator EstimatesKeystroke determined by typing speed0.28s for average typist (40 wpm), 0.08s for fast typist (155 wpm), 1.20s for worst typist

Pointing determined by Fitts’ Law (or general approximation)T = a + b log (d/s +1) ORT = 1.1s

Drawing determined by Steering LawT = a + b (d/s)

Operator EstimatesHoming estimated by measurementT = 0.36s (between keyboard and mouse)

Mental prep estimated by measurementT = 1.35s(estimated by taking the total task time, subtracting physical operator time, and dividing by the number of “chunks” of activity)

Adapted from Rob Miller

Example: Deleting a WordUsing Shift-Click

MP [start of

word]K [click]MP [end of word]K [shift]K [click]H [to keyboard]MK [Del]

Total: 3M + 2P + 4K= 7.37 sec

Using DeleteMP [start of word] K [click]HMK [Del] x n [length of word]

Total: 2M + P + H + (n+1) K= 4.44 + 0.28n sec

In-class ExerciseGenerate a KLM model for deleting a file from your desktop

Estimate the time it would take using the provided operator times

Compare the predicted time with the actual time

48

Example

Consider the searching a Word document for all occurrences of a four-letter word, and replacing it with another four-letter word.

49

Reach for mouse H[mouse] 0.40Move pointer to "Replace" button P[menu item] 1.10

Click on "Replace" command K[mouse] 0.20

Home on keyboard H[keyboard] 0.40Specify word to be replaced M4K[word] 2.15

Reach for mouse H[mouse] 0.40Point to correct field P[field] 1.10Click on field K[mouse] 0.20Home on keyboard H[keyboard] 0.40Type new word M4K[word] 2.15Reach for mouse H[mouse] 0.40Move pointer on Replace-all P[replace-all] 1.10

Click on field K[mouse] 0.20Total 10.2

50

Error Messages Blame the system, not the user

“Unrecognized” vs. “illegal” command Easy error recovery Can have multiple levels of messages E.g. in XXX product, “can't save file” — why

not?

Problem: Geek-speak: Refers to “Print dialog”, a technical UI component term

Microsoft Word 98Print Status Dialog Box

Microsoft Word 98Print Status Dialog Box

Problem: Two buttons (stop/cancel) to end the print??

Eudora Pro 4.0 Special menu

Problem: What’s the difference between Find and Search?

Virus Scan 3.0.3 Warning

Problem: Careless writing. Note typo -- “more that”

Microsoft Notepad Menu

Problem: No keyboard equivalents

Microsoft Windows Ports Control Panel

Problem: Dialog box control buttons mixed with setting and help buttons

CS5540

Eudora Version Installation Dialog Box

Problem: Traps user: no way to Cancel installation at this point. Gives options for bad modes.

CS5540 58

SpellTools User Dictionary

…Problem: No “...” on Import button

CS5540 59

Oracle’s ORS CLEATS web-application

Problem: Should write out “Pin Number,” not “Pin No”

Unsubscribe from mailing list

Problem: Silly message

61

Bad Error Messages

62

More bad error messages!

63

Another Bad Example

http://stinet.dtic.mil/

64

Another Bad Example

65

Another Bad Example

66

Pretty Good Example Pretty Good: travel.yahoo.com: Says what to do to fix it

But language is inconsistent

67

Help and Documentation True walk up and use? Most people will not read documentation

If do, then First time product is used, or else In a panic, so need information right away

Iterative design of documentation needed SuperBook application answer found in 4.3 minutes,

compared to 7.6 minutes before fixing Help system is an extra feature to learn “Help doesn’t”

If need to add help, maybe fix the feature? Use documentation writers to help refine the system

Good quality writing

68

Good Help Example

NSFreportsystem What

& Why

69

Firefox: No Zoom Indicator

70

Worst interfaces

72

Kitchen timer

73

Turn down the TV

74

Xerox Real Business (worst 2011)

Examples of non-usable systems

EclipseHard learning curve, bad for beginnersToo many windows, confusing layout, too much going on (advanced options)

ISIS pops up a window, pop-up blocker problems can’t use browser’s back button gives course instructor number instead of name must enter schedule-number instead of clicking on course ID and

number Must use semester as a code, and if you get this wrong it’s

confusing what’s wrong Interface has pictures/images for links, not the conventional

under-lined links not integrated into COD, so must copy info over from COD to

ISIS Kicks you off too quickly Too often overloaded, too many users Unavailability at certain hours / don’t know when it’s unavailable /

status not visible easily Links on main page are too similar SSN number use

77

175 design Guidelines These are primarily intended to guide you to a good design, not to be used for

evaluation1) Help users plan goals, tasks2) Provide a clear model of how users view system in terms of tasks3) Help users with system model, metaphors, work context4) Design to match user’s conception of high-level task organization5) Help users understand what system features exist and how they can be used in their

work context6) Help users decompose tasks logically7) Make clear all possibilities for what users can do at every point8) Keep users aware of system state for planning next task9) Keep the task context visible to minimize memory load10) Help users plan the most efficient ways to complete their tasks11) Keep users aware of task progress, what’s been done and what’s left to do12) Provide cognitive affordances at the end of critical tasks to remind users to

complete the transaction13) Provide effective cognitive affordances that help users get access to system

functionality14) Help users know/learn what actions are needed to carry out intentions

Quoted from Chapter 19 of H. Rex Hartson and Pardha S. Pyla, The UX Book: Ensuring a Quality User Experience, to be published by Morgan Kaufmann / Elsevier in 2011.

Guidelines, cont.15) Help users know how to do something at action/object level16) Help users predict outcome of actions17) Help users determine what to do to get started18) Provide a cognitive affordance for a step the user might forget19) Support user with effective sensory affordances in presentation of cognitive

affordances20) Make cognitive affordances visible21) Make cognitive affordances noticeable22) Make text legible, readable23) Control cognitive affordance presentation complexity with effective layout,

organization, and grouping24) Present cognitive affordance in time for it to help the user before the

associated action25) Help user determine actions with effective content/meaning in cognitive

affordances26) Design cognitive affordances for clarity27) Use precise wording in labels, menu titles, menu choices, icons, data fields28) Use a verb and noun and even an adjective in labels where appropriate.29) Avoid vague, ambiguous terms. 78


Guidelines, cont.30) Be as specific to the interaction situation as possible31) Clearly represent work domain concepts32) Use dynamically changing labels when toggling33) Provide cognitive affordances to indicate formatting within data fields34) Constrain the formats of data values to avoid data entry errors35)Provide clearly marked exits36)Provide clear “do it” mechanism37)Be predictable; help users predict outcome of actions with feed-forward

information in cognitive affordances38)Make choices distinguishable39)Be consistent with cognitive affordances40)Use consistent wording in labels for menus, buttons, icons, fields41)Use similar names for similar kinds of things42)Do not use multiple synonyms for the same thing43)Use the same term in a reference to an object as the name or label of the

object44)Use different terms for different things, especially when the difference is

subtle 79Quoted from Chapter 19 of H. Rex Hartson and Pardha S. Pyla, The UX Book: Ensuring a Quality User Experience, to be published by Morgan Kaufmann / Elsevier in 2011.

Guidelines, cont.

80

45) Be consistent in the way that similar choices or parameter settings are made

46) Decompose complex instructions into simpler parts47) Use appropriate layout and grouping by function to convey content and

meaning48) Group together objects and design elements associated with related tasks

and functions49) Do not group together objects and design elements that are not associated

with related tasks and functions50) Support user choices with likely and useful defaults51) Provide the most likely or most useful default selections52) Offer most useful default cursor position53) Relieve human short term memory loads by maintaining task context

visibly or audibly for the user54) Support human memory limits with recognition over recall55) Avoid requirement to retype or copy from one place to another56) Support special human memory needs in audio interaction design57) Avoid cognitive indirectness58) Be complete in your design of cognitive affordances; include enough

information for users to determine correct actionQuoted from Chapter 19 of H. Rex Hartson and Pardha S. Pyla, The UX Book: Ensuring a Quality User Experience, to be published by Morgan Kaufmann / Elsevier in 2011.

Guidelines, cont.

81

59) Prevent loss of productivity due to hesitation, pondering60) Use enough words for unambiguous labels61) Add supplementary information, if necessary62) Give enough information for users to make confident decisions63) Give enough alternatives for user needs64) Employ usage-centered wording, the language of the user and the work

context, in cognitive affordances65) Find ways to anticipate and avoid user errors in your design66) Help users avoid inappropriate and erroneous choices67) Disable buttons, menu choices to make inappropriate choices unavailable68) Gray out to make inappropriate choices appear unavailable69) But help users understand why a choice is unavailable70) Provide a clear way to undo and reverse actions71) Offer constructive help for error recovery72) Avoid confusing modalities73) Distinguish modes clearly74) Use “good modes” where they help natural interaction without confusion75) Support human memory limitations in the design of task structure76) Support user with effective task structure and interaction control77) Provide alternative ways to perform tasks


Guidelines, cont.

82

78) Provide shortcuts79) Provide logical grouping in layout of objects80) Group together objects and functions related by task or user work activity81) But avoid grouping of objects and functions if they need to be dealt with

separately82) Support task thread continuity by anticipating the most likely next task,

step, or action83) Make the most of user’s work84) Do not requiring users to re-enter data85) Retain user state information86) Avoid the feeling of loss of control87) Give direct manipulation support88) Always provide a way for the user to “bail out” of an on-going operation89) Support users making physical actions with effective sensory affordances

for sensing physical affordances90) Support user with effective physical affordances for manipulating objects,

help in doing actions91) Avoid physical awkwardness92) Accommodate physical disabilities93) Design layout to support manual dexterity and Fitts’ law


Guidelines, cont.

83

94) Support targeted cursor movement by making selectable objects large enough

95) Group clickable objects related by task flow close together96) But not too close, and do not include unrelated objects in the grouping97) Design physical movement to avoid physical overshoot98) Include physicality in your design when the alternatives are not as

satisfying to the user99) Check your functionality for missing features100)Check your functionality for non-user-interface software bugs101)Avoid too much automation and loss of user control102)Help the user by automating where there is an obvious need103)Provide feedback for all user actions104)Provide progress feedback on long operations105)Request confirmation as a kind of intervening feedback106)But don’t overuse and annoy107)Support user with effective sensory affordances in presentation of

feedback108)Make feedback visible109)Make feedback noticeable110)Locate feedback within the user’s focus of attention


Guidelines, cont.

84

111) Make feedback large enough to notice112)Make text legible, readable113)Control feedback presentation complexity with effective layout,

organization, and grouping114)Help users detect error situations early115)Maintain a consistent appearance across similar kinds of feedback116)Maintain a consistent location of feedback presentation on the screen to

help users notice it quickly.117)Use the most effective feedback presentation medium118)Consider audio as alternative channel119)Help users understand outcomes with effective content/meaning in

feedback120)Design feedback for clarity121)Support clear understanding of outcome (system state change), so users

can assess effect of actions122)Give clear indication of error conditions123)Be complete in your design of feedback; include enough information for

users to fully understand outcomes and be either confident that their command worked or certain about why it didn’t

124)Prevent loss of productivity due to hesitation, ponderingQuoted from Chapter 19 of H. Rex Hartson and Pardha S. Pyla, The UX Book: Ensuring a Quality User Experience, to be published by Morgan Kaufmann / Elsevier in 2011.

Guidelines, cont.

85

125)Add supplementary information, if necessary126)Give enough information for users to make confident decisions about the

status of their course of interaction127)Help users understand what the real error is128)Give enough information about the possibilities or alternatives so user can

make an informed response to a confirmation request129)Design feedback wording, especially error messages, for positive

psychological impact130)Make the system take blame for errors131)Be positive, to encourage132)Provide helpful, informative error messages, not “cute” unhelpful messages133)Employ usage-centered wording, the language of the user and the work

context, in displays, messages, and other feedback134)Be consistent with feedback135)Label outcome or destination screen or object consistently with starting

point and action136)Organize feedback for ease of understanding137)Provide user control over amount and detail of feedback138)Give only most important information at first; more on demand


Guidelines, cont.

86

139)Organize information displays for ease of understanding140)Eliminate unnecessary words141)Group related information142)Control density of displays; use white space to set off143)Columns are easier to read than wide rows144)Use abstraction per Shneiderman’s “mantra”: Overview first; zoom and

filter; details on demand145)Employ usage-centered wording, the language of the user and the work

context146)Avoid the use of anthropomorphism in interaction designs147)Avoid using first-person speech in dialogue148)Avoid condescending offers to help149)Avoid poor attempts at humor150)Avoid violent, negative, demeaning terms151)Avoid use of psychologically threatening terms, such as “illegal”, “invalid”,

“abort”152)Avoid use of the term “hit” instead of “press” or “click”153)Avoid irritation with annoying sound and color in displays154)Use color conservatively155)Use pastels, not bright colors


Guidelines, cont.

87

156)Be aware of color conventions (e.g., avoid red, except for urgency)157)Watch out for focusing problem with red and blue158)Avoid fancy or cute design without a real purpose159)Make presentation of text legible160)Make font size large enough for all users161)Use good contrast with background162)Use mixed case for extensive text163)Avoid too many different fonts, sizes164)Use legible fonts165)Use color other than blue for text166)Accommodate sensory disabilities and limitations167)Allow user settings, preference options to control presentational

parameters168)Accommodate different levels of expertise/experience with preferences169)Don’t let affordances for new users be performance barriers to experienced

users170)Be helpful with Help171)Do not try to achieve the appearance of simplicity by just reducing

usefulness172)Organize complex systems to make the most frequent operations simple


Guidelines, cont.

88

173)Use consistent layout/location for objects across screens174)Maintain custom style guides to support consistency175)Use structurally similar names and labels for objects and functions that are

structurally similar176) ….and the list isn’t even finished


1 evaluation / usability usability is it a “good” interface? in what ways? usability: how well...

Documents